Both of base campaigns have choice point on fourth scenario. You can save just before choice point to play both of them. X master means you must have X adept.
Evil choice - kill humans/Laryssa in Elven/Commonwealth campaign on fourth scenario
Good choice - just don't exterminate them.
You can pick Grey Guard or Shadowborn specialization on second scenario of necromancers campaign
Elven Court
1. High Elf Rogue, Creation + Water Adept and Explorer
2. Draconian Archdruid, Creation Master and Destruction Adept
3. Goblin Theocrat, Air Master and Expander
4. High Elf Rogue, Creation + Water Adept and Explorer
5e. Orc Sorcerer, Fire Master and Air Adept
6e. High Elf Rogue, Creation + Water Adept and Explorer
5g. Dwarf Dreadnought, Earth Master and Creation Adept
6g. High Elf Rogue, Creation + Water Adept and Explorer
The Commonwealth
1. Human Dreadnought, Fire Master and Expander
2. Human Sorcerer, Water Master and Air Adept
3. High Elf Warlord, Master of Air and Earth Adept
4. Human Dreadnought, Fire Master and Expander
5e. Dwarf Theocrat, Destruction Master and Earth Adept
6e. Human Dreadnought, Fire Master and Expander
5g. Orc Rogue, Air + Earth + Water Adept
6g. Human Dreadnought, Fire Master and Expander
Golden Realms
1. Halfling Warlord, Water Master and Partisian
2. Halfling Sorcerer, Wild Magic Master and Air Adept
3. Halfling Theocrat, Creation Master and Water Adept
Necromancer Campaign
1. Frostling Necromancer, Earth + Fire + Destruction Adept
2. Tigran Archdruid, Keeper of Peace Master + Water Adept
3. Frostling Necromancer, Grey Guard OR Shadowborn Master + Fire Adept